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Leiden experimental physicist Dirk Bouwmeester is responsible for a number of significant breakthroughs in quantum mechanics. His European research group is also working on a new DNA detection technique and hopes to drastically improve fusion reactors.

Dirk Bouwmeester was in the US when he heard that he had been awarded the Spinoza Prize: ‘I was really amazed. I am incredibly grateful to everyone who supported my nomination.’ Bouwmeester divides his time between Leiden University and the University of California in Santa Barbara.

‘No, my research requires both locations. Leiden for temperatures near absolute zero, and Santa Barbara for the fabrication of nanostructures.’ His group is building a minuscule mirror which should literally be able to be simultaneously in two positions– in quantum theory jargon: in a superposition of two states. This bizarre phenomenon was already observed long ago for free electrons and atoms; in fact quantum theory as a whole would not work without particles in superposition. But the mirror, however small it is, still consists of billions of atoms, and is therefore considered to be a macroscopic object, and the question is whether such objects can actually be in superposition. If this works, it will involve a temperature of maximum 300 nanokelvin, 0.0000003 degrees above absolute zero (-273 degrees Celsius).
Bouwmeester: ‘This mirror explores the limits of quantum theory, and investigates whether such limits actually exist.’

‘We recently also started a collaboration with the Human Genetics department of the LUMC. We are developing so-called silver clusters on DNA or RNA. These clusters consist of only 5 to 10 silver atoms and they can emit light. In addition, the colour of the light depends on the DNA structure, and it changes when the DNA attaches to something, for instance to other DNA. Such silver clusters can therefore be used as optical labels in a living cell. On the basis of the changes in colour, we can see whether something is changing in the DNA or its immediate environment. Together with biophysicists and physicians, I want to investigate the possible applications of these unique dynamic optical labels.’

Knotted plasma, light and magnetic fields
‘A completely different project is the ‘tying up into knots’ of plasma, light and magnetic fields. So far this was only a theoretical possibility based on natural laws, but two years ago, we started to experiment with shining light on a plasma – a red-hot gas – with ring-shaped laser beams in order to make it possible in practice. We now also have a good simulation programme which shows that such structures, with knotted magnetic field lines, can be very stable.'

'For the silver clusters, I would like to strengthen our collaboration with the LUMC, in particular with the group that is searching for a treatment for Duchenne muscular dystrophy, a hereditary disease. In short, this group is developing a kind of DNA patch to cover the patient’s faulty DNA, and optical labels may help to really customise this treatment.

Possibilities of nuclear fusion
‘The magnetic stability of a plasma is very important for nuclear fusion. This field is dominated by incredibly large-scale projects, such as the European fusion reactor ITER. The larger the reactor, the easier it is to keep the plasma under control with magnetic fields. Nevertheless, in some cases the plasma still becomes unstable and damages the wall of the reactor.
‘If we can make these magnetic fields that are tied into plasma a reality, this may have momentous consequences, because we will be able to build much smaller fusion reactors. I think that this might open up the very real possibility of using a fusion reactor to power planes, and maybe even spacecraft.’

‘The most expensive project, the one involving the nano mirror, is in the most advanced stage. We are now ready for the seventh generation of mirror and suspension. The two newest generations meet the mechanical requirements, but the major obstacle now is the suppression of vibrations from the environment. These vibrations slightly warm up the mirror. I expect that within a year, we will be able to lower the temperature to the required 300 nanokelvin, which is a very important milestone for this project. There is too much uncertainty at this point to be able to predict how long it will take to show that the mirror is really in superposition.’